1. Field of the Invention
The present invention relates to an optical pickup for use in a disk player such as a DVD player.
2. Description of the Related Art
FIG. 16 shows an example of an optical pickup in the related art. This optical pickup is configured as follows. That is, a beam passage hole 2 with a half mirror HM penetrates a base 1 made of synthetic resin. A photodiode PD is disposed in an opening portion 2a at one end of the beam passage hole 2 while a collimator lens QWP and an objective lens OL are disposed in an opening portion 2b at the other end of the beam passage hole 2. A laser diode LD and a diffraction grating G are disposed in a laser hole 3 communicating with the beam passage hole 2. A laser beam from the laser diode LD is projected onto a disk D through the diffraction grating G, the half mirror HM, the collimator lens QWP and the objective lens OL. The beam reflected from the disk D is received by the photodiode PD through the half mirror HM so that information recorded in the disk D can be read.
In the related art, there is a structure for supporting the diffraction grating G, as disclosed in JP-A-2-218028. An example of such a structure will be described with reference to FIGS. 17 and 18. A diffraction grating operating hole 30 is provided in a laser hole side wall portion 1A of the base 1 so as to penetrate the laser hole side wall portion 1A. In an adjustment process prior to shipment, an operating rod 31 inserted into the operating hole 30 is brought into contact with the outer circumferential surface of the diffraction grating G so as to rotate the diffraction grating G at a predetermined angle. Thus, the laser beam is dispersed desirably. After that, the diffraction grating G is bonded to the laser hole side wall portion 1A by an adhesive agent.
The procedure for molding the laser hole side wall portion 1A will be described with reference to schematic views shown in FIGS. 19A–19C. As shown in FIG. 19A, a core 34 is inserted into a mold 33. A slide pin 35 having the same diameter as that of a lock hole disposed in a slide hole 33a of the mold 33 is advanced to abut against the core 34. Synthetic resin is charged into an air gap 36 between the mold 33 and the core 34 so as to form the laser hole side wall portion 1A as shown in FIG. 19B. After that, the slide pin 35 is retracted, and the core 34 is extracted from the mold 33. Then, the base 1 having the laser hole side wall portion 1A with the operating hole 30 as shown in FIG. 19C is extracted from the mold 33.
In the configuration, the mold 33 with the slide pin 35 is required for molding the laser hole side wall portion 1A provided with the operating hole 30 penetrating the laser hole side wall portion 1A. Thus, the mold costs due to such a complicated structure. In addition, the molding cycle becomes complicated due to the operation of the slide pin 35. Thus, the cycle time becomes so long that the working efficiency deteriorates correspondingly. Further, even when necessity to repair the diffraction grating G due to an error in adjustment or the like occurs after the diffraction grating G has been bonded, the diffraction grating G cannot be extracted.
In addition, since the laser diode LD is pressed into the laser hole 3 of the base 1, not only the laser diode LD but also the diffraction grating G and the base 1 have to be abandoned when the laser diode LD is condemned as a defective product in examination prior to shipment. Thus, the cost for abandonment increases. In addition, the cost of material is indeed reduced due to the base 1 molded out of synthetic resin. But the radiating effect of the synthetic resin is so small that the base 1 may be deformed due to thermal expansion caused by the heating of the laser diode LD. Thus, there is a fear that an optical axis O connecting the photodiode PD and the objective lens OL may be bent to cause a reading error.